"JSW08 Poster Nelson 202 37"
Interdisciplinary studies of CDOM in the global ocean Norman B. Nelson 1, Chantal M. Swan 1, David A. Siegel 1, Craig A. Carlson 1,2 1Institute for Computational Earth System Science, 2Dept. Ecology, Evolution and Marine Biology, University of California, Santa Barbara Overview Global distribution and dynamics of CDOM in the surface and deep ocean We are currently engaged in several research efforts concerned with the distribution, dynamics, and characterization of chromophoric dissolved organic matter (CDOM) in the global ocean. These include: Norm Nelson, Dave Siegel, Craig Carlson •Ocean color algorithm development for retrieving CDOM absorption as well as chlorophyll and EUCFe 2006 Remote sensing of CDOM distributions in surface waters over the global CDOM Cycling Box Models AMMA particulate backscatter in surface waters (with Stephane Maritorena). This has led us to new insight 2006 ocean highlight a superficial correlation with chlorophyll and productivity, but concerning the influence of CDOM on retrieval of chlorophyll as well as pointing toward research on the with some significant differences. Significant CDOM in upwelling zones raised In these flow charts, the straight yellow arrows represent advective fluxes of CDOM (including EqBOX the question of whether CDOM was present in the ocean interior, if so what horizontal transport, upwelling, and downwelling), curled arrows represent local production of nature of CDOM cycling. 2005 2006 controlled its abundance in the deep sea, and how are the surface and interior CDOM, and the red arrows represent photobleaching. The top row of boxes represent surface •Time-series study of apparent and inherent optical properties at the BATS site southeast of Bermuda in coupled. We are in the process of conducting a global field survey of CDOM waters, and the second row represents the main thermocline down to 1 km. The color the subtropical North Atlantic. Our results have revealed a seasonal cycle in CDOM distribution that distribution and characteristics relative to hydrography, optics, and selected corresponds to CDOM absorption coefficient (as in the section plot to the left). indicated photolysis was the main sink, and secondary production the main source. biological parameters, as an ancillary project on the U.S. CO2/CLIVAR Repeat Hydrography surveys. Since 2003 we have collected data on meridional sections covering the full range of surface CDOM in every open ocean basin. CDOM Dynamics: Atlantic •Photochemistry of CDOM: Measuring quantum yields for bleaching and photoproduction of CDOM on samples collected from the field in low CDOM areas where these rates are difficult to measure. Completed (full measurement set including CDOM, microbes, optics) Our results have highlighted the importance of thermohaline circulation and North Atlantic Subtropics EQ Subtropics South Atlantic Completed (limited measurement set, CDOM and hydrography) Our results are leading to new insights concerning the nature and cycling of CDOM in the global ocean. remineralization in determining the abundance of CDOM in the deep ocean. In Future (in planning) Ongoing and future efforts include characterization of CDOM along gradients of ventilation age, mixing, and the Atlantic, rapid meridional overturning mixes CDOM more homogenously, photolysis using optical and chemical methods, and incorporation of CDOM terms into mixed layer and rapidly transmitting surface CDOM concentrations to the interior. In the North general circulation models. In surface waters, the distribution of CDOM is easily explained by a Pacific and Indian Ocean, slow mixing allows accumulation of CDOM formed balance between production and photolysis. In subtropical waters as a result of remineralization. In the Southern Ocean, low production at the persistent stratification and net downwelling leads to low CDOM surface and rapid ventilation transmit low CDOM signals to the interior, Mode Water Mode Water concentrations. Formation of subtropical mode water in regions with creating the interhemispheric imbalance reflected in remotely sensed data. Bermuda Bio-Optics Project: Decadal scale observations seasonal mixed layers carries low CDOM water to the ocean interior, Norm Nelson, Dave Siegel where a low CDOM signature is easily observed in the mode waters of Arctic To the North and South Atlantic. Meridional sections across the Equator ACC clearly shows the transport of CDOM to the surface where it is bleached. Rapid meridional overturning allows little CDOM accumulation The contribution of CDOM to ocean color variability not related to Advection + bleaching balances net production An outstanding question: is the high CDOM observed in the North chlorophyll abundance was first Atlantic a residual of terrestrial CDOM from the Arctic? We hope to suggested by Siegel and coworkers studying the first year (1992) of in situ resolve this with ongoing research and a repeat of the 2003 North CDOM Dynamics: Pacific / Indian acdom (325 nm, m-1) Atlantic sections in 2011-2012. radiometry data from the Bermuda Bio- Optics Project, a time-series study of North Pacific Subtropics EQ Subtropics Southern O. optical properties in the water column piggybacking on the successful acdom (443 nm, m-1) Bermuda Atlantic Time-series Study cruises. Since 1994 the real contribution of Mode Water CDOM to ocean color has been assessed using spectrophotometric From measurements of CDOM absorption ACC spectra, as part of an integrated study of component absorption. Sustained observations of CDOM are North: Long residence time allows CDOM accumulation being considered in the context of South: Production limited (iron?) Low surface signal carried climate-related changes in the factors controlling CDOM abundance. (Global CDOM map from SeaWiFS/GSM, mission mean) to depth by advection / water mass formation At BATS, seasonal mixing homogenizes the CDOM Quantum yield () of CDOM photolysis -- the major sink of CDOM Photobleaching / photoproduction quantum yields profile from a characteristic summer pattern that Chantal Swan, NASA Earth System Science Fellowship includes a surface minimum, a local maximum in the Sample Site Latitude Region Depth T (°C) Sal. Chl-a Initial aCDOM Initial aCDOM (325nm,325nm) (440nm,440nm) Total (m) (ppt) (ug/l) (m-1) at (m-1) at (m2 mol (m2 mol irradiation 60-150m range, and a local minimum in the mode • Photolysis moderates global surface distribution of CDOM photons-1) photons-1) 325nm 440nm time (days) water. But this mean pattern summarizes much variability. We are examining interannual patterns in PB189S5 34°N Coastal Pacific 0 16 33.1 0.600 0.20 0.02 -0.08 -0.004 2.02 CDOM distribution in the upper water column to assess • (and photolysis rate) can be used in concert with upper ocean vertical mixing rate to deduce (So. Cal. Bight) the relative contribution of local effects (production, microbial production rate of CDOM (a term otherwise hard to measure) BATS 32°N Subtropical N. Atlantic 80 23 36.6 0.200 0.06 0.001 -0.05 -0.001 3.02 mixing) versus remote effects (mode water formation, P16NS51 29°N Subtropical 140 19 35.2 0.078 0.07 0.003 -0.09 -0.002 2.97 overall irradiance leading to photolysis). An intriguing • Constraining a mixed-layer budget of CDOM will permit its use as the first remotely-sensed tracer of N. Pacific hint of CDOM-climate teleconnections can be seen in a P16NS51 29°N Subtropical 40 20 35.3 0.096 0.05 0.001 -0.05 0 3.06 correlation between the North Atlantic Oscillation and upper ocean circulation N. Pacific CDOM abundance at 160 m. P16NS76 55°N Subarctic 200 4 33.9 0.004 0.17 0.02 -0.07 0.004 2.00 Key Findings: P16NS76 55°N Pacific Subarctic 80 3 33.0 0.019 0.14 0.01 -0.03 0.009 2.00 Pacific Acknowledgments: Publications 2007-08 • Loss of CDOM absorption in the UV due to full-spectrum solar irradiation occurs in nearly all regions P16NS19 0.5°N Equatorial 100 22 35.6 0.060 0.06 0.005 -0.05 0.015 2.95 Pacific NASA Ocean Biology and Biogeochemistry Goldberg, S.J., D.A. Hansell, N.B. Nelson, D.A. Siegel, and C.A. Carlson, (submitted to sampled. We can constrain environmental range of open ocean photolysis P16SS61 46°S Subantarctic Pac. 80 10 34.4 0.242 0.07 0.01 0 0.012 2.06 NSF Chemical Oceanography Deep-Sea Research I). Temporal dynamics of dissolved combined neutral sugars and the Frontal Zone U.S. CLIVAR/CO2 Repeat Hydrography Project quality of dissolved organic matter in the northwestern Sargasso Sea. P16SS61 46°S Subantarctic Pac. 0 13 34.4 0.132 0.05 0.01 0 0.008 3.01 (Jim Swift, Lynne Talley, Dick Feely, Rik Wanninkhof, Nelson, N. B., D. A. Siegel, C. A. Carlson, C. Swan, W. M. Smethie, S. Khatiwala • 50% of regions sampled show a very unexpected concurrent phenomenon at longer wavebands: Frontal Zone Rana Fine) (2007). Hydrography of chromophoric dissolved organic matter in the North Atlantic. formation of CDOM due to irradiation UCSB Field Teams: Dave Menzies, Jon Klamberg, DeepĞ Sea Research I. doi:10.1016/j.dsr.2007.02.006 Table: Summary of associated hydrographic data and calculated values (325nm and 440nm, shaded blue). Sites and values marked in red Meredith Meyers, Ellie Wallner, Meg Murphy, Natasha denote where (440nm;440nm) is positive, corresponding to observed photoproduction of CDOM during irradiation. Swan, C. M., N. B. Ne lson, D. A. Siegel, C. A. Carlson, E. Nasir (to be submitted to McDonald Deep-sea Research I). Biogeochemistry of chromophoric dissolved organic matter in the Schematic of inversion terms using Subtropical N. Atlantic (BATS) example: Hansell Group: Dennis Hansell, Charlie Farmer, Pacific. Wenhao Chen daCDOM/dt (measured) E0*ācdom E0*ācdom*(o=325nm) • (o=325nm) has distinct range over all irradiation Bill Landing (FSU) and Chris Measures (UHI) (Water Presentations2007-08 wavelengths in regions sampled samples) Time Nelson, N. B., D. A. Siegel, C. A. Carlson, C. M. Swan, S. J. Goldberg (2008). Invited Bill Smethie & Samar Khatiwala, LDEO (CFC ages) Talk, ASLO Ocean Sciences, Orlando, FL: CDOM in the deep sea: distribution and Time • What are the controls on ? Ru Morrison & Mike Lesser, UNH (MAA analysis) dynamics from trans-ocean sections. Wilf Gardner and Team, TAMU (C-Star Swan, C. M., D. A. Siegel, N. B. Nelson, T. S. Kostadinov (2008). Poster, ASLO Ocean Initial aCDOM explains roughly half of the variance in transmissometer) Mike Behrenfeld and Team, OSU (Equatorial BOX Sciences, Orlando, FL: Photochemical cycling of chromophoric dissolved organic matter (r2=0.56, n=18) (CDOM) in the open sea: Comparison of photolytic quantum yields among ocean project) regions. (See attached 08_ASLO_poster_S wan.pdf) Erica Key and Team, U Miami (AMMA-RB 2006) In situ temperature does not explain any variance in Swan, C. M., N. B. Ne lson, D. Siegel, C. A. Carlson (2007). Talk, ASLO Aquatic Time Jim Murray and Team, UW (EUCFe 2006) Sciences, Santa Fe, NM: Hydrography of chromophoric dissolved organic matter (r2=0.02, n=18) R/Vs Brown, Knorr, Revelle, Melville, Thompson, Ka’I, (CDOM) in the Pacific Ocean. Kilo Moana